The fourth battle of Kawanakajima resulted in greater casualties for both sides, as a percentage of total forces, than any other battle in the
Sengoku period and is, according to Turnbull, one of the most tactically interesting battles of the period. After besieging
Hōjō Ujiyasu's
Odawara castle, Uesugi Kenshin was forced to withdraw after hearing rumors about the movement of Takeda Shingen's army. In September 1561 Kenshin left his
Kasugayama Castle with 13,000 warriors, determined to destroy Shingen. He left some of his forces at
Zenkō-ji but took up a position on Saijoyama, a mountain to the west of, and looking down upon, Shingen's
Kaizu castle. To Kenshin's ignorance, the Kaizu castle contained no more than 150 samurai and their followers and he had taken them completely by surprise. However, the general in command of the castle,
Kosaka Masanobu, through a system of signal fires, informed his lord, in Tsutsujigasaki fortress, 130 km away in
Kōfu, of Kenshin's move. , woodblock print by
Utagawa Kuniyoshi (1847–48). Wounded and believing his strategy had failed, Kansuke retired to a nearby hill and committed suicide. Shingen left Kōfu with 16,000 men, acquiring 4,000 more as he traveled through
Shinano Province, approaching Kawanakajima on the west bank of the Chikumagawa (
Chikuma River), keeping the river between him and Saijoyama. "Neither army made a move", knowing that victory would require the essential element of surprise. Shingen was thus allowed into his fortress at Kaizu along with his
gun-bugyō (army commissioner),
Yamamoto Kansuke. At that time Kansuke formed a strategy that he believed would prove effective against Kenshin. Kōsaka Masanobu left Kaizu with 8,000 men, advancing up Saijoyama under cover of night, intending to drive Kenshin's army down to the plain where Takeda Shingen would be waiting with another 8,000 men in
kakuyoku ("crane's wing"), formation. However, whether via spies in Kaizu or scouts looking down from Saijoyama, Kenshin guessed Shingen's intentions and led his own men down to the plain. Kenshin descended from Saijoyama by its western flanks. Instead of fleeing Kosaka's dawn attack, Uesugi Kenshin's army crept down the mountain, quietly using bits of cloth to deaden the noise of their horses' hooves. With the beginning of dawn, Shingen's men were surprised to find Kenshin's army ready to charge at them—as opposed to fleeing from the mountain, as expected. Uesugi's forces attacked in waves, in a
kuruma gakari formation, in which every unit is replaced by another as it becomes weary or destroyed. Leading the Uesugi vanguard were two of Uesugi's "Twenty-Eight Generals",
Kakizaki Kageie and
Irobe Katsunaga. Kakizaki's unit of mounted samurai clashed with
Takeda Nobushige's unit, resulting in the death of Nobushige, younger brother of Shingen. While the
kakuyoku formation held surprisingly well, the Takeda commanders eventually fell, one by one. Seeing that his pincer plan had failed,
Yamamoto Kansuke charged into the enemy ranks, being killed in action with his two chief retainers,
Osaragi Shōzaemon and
Isahaya Sagorō. Eventually the Uesugi forces reached the Takeda command post, and one of the most famous single combats in Japanese history ensued.
Uesugi Kenshin himself burst into the headquarters, attacking
Takeda Shingen who, unprepared for such an event, parried with his
signalling fan as best as he could, and held Kenshin off long enough for one of his retainers, Hara Osumi-no-Kami, to spear Kenshin's mount and drive him off. The Takeda main body held firm, despite fierce rotating attacks by the Uesugi.
Obu Saburohei fought back against Kakizaki's samurai.
Anayama Nobutada destroyed
Shibata Harunaga of Echigo, and forced the Uesugi main force back to the Chikumigawa. Meanwhile, Kosaka's stealth force reached the top of Saijoyama and, finding the Uesugi position deserted, hurried down the mountain to the fort, taking the same path they had expected the fleeing Uesugi to take. After desperate fighting, they punched their way through the 3000 Uesugi warriors defending the fort (under the command of Uesugi general
Amakasu Kagemochi), and pressed on to aid Takeda's main force. The Kosaka force then attacked the retreating Uesugi from the rear. Takeda Shingen's many great generals, including his younger brother Takeda Nobushige and
Murozumi Masakiyo, were killed in the field.
Result In the end, it is told that the Uesugi army suffered 62% casualties, while the Takeda lost 72%. The chronicles seem to indicate that the Takeda made no effort to stop the Uesugi from retreating after the battle, burning the encampment at Saijoyama, returning to Zenkō-ji and then to
Echigo Province. Some more conservative estimates place the casualties around 20%. ==Fifth battle ==